Electrolytic production of alloys



W. w. SHROPSHIRE ETAL 2,341,244

INVENTORS Slvw M m L-l uzm ATTORNEYS unsuitable for discriminating use.

Patented Feb. 8, 1944 ELECTROLYTIC PRODUCTION OF ALLOYS William WallaceShropshire, Chicago, and Amson L. Frohman, Calumet City, 111., assignorsto International Smelting 8a Refining Company, New York, N. Y., acorporation of Montana Application July 11, 1939, Serial No. 283,832

4 Claims.

This invention relates to the production of .alloys, particularlylead-base alloys, and has for its object the provision of an improvedmethod of producing alloys of leadwith metals having a substantiallyhigher melting temperature than lead.

For certain applications, alloys of lead containing small amounts ofsuch metals as copper, nickel, tellurium, silver and the like possessdesirable properties and characteristics not found in substantially purelead. For example, it is known that the addition of approximately .06%by weight of copper, to refined lead forms an alloy possessing greatertensile strength and greater resistance to certain types of corrosionthan ordinary copper-free lead. It is also known that the addition of asmall amount of nickel'or tellurium or silver or other metals orcombinations of these metals to lead forms alloys having desirablecharacteristics for various applications.

The amount of the alloying metal which is required to impart to lead thedesired beneficial properties is usually very small. Further, thedesired advantages are not gained unless the alloying metal or metals isuniformly and thoroughly'dispersed throughout the mass of lead.

It is diflicult to produce an alloy by melting together metallic leadand one or more of the higher melting point metals. Where such aprocedure is used, the metallic lead must be raised to an abnormallyhigh temperature and the alloying metal or metals must'be added in afinely divided state. The alloys produced are usually not uniform incomposition whiich renders them There is'also a large amount of oxidizedmaterial produced which must be retreated at additional expense.

Such lead base alloys are also made by chemical methods, whereby themetal or metals to be alloyed with the lead are contained in salts,which are added to the surface of a bath of molten lead. These methodsdepend upon the higher heat of combination or lead with the acid radicles of the salts than the heat of combination of these acid radicleswtih the metal or metals of the addition salt. As a result of these saltadditions, a chemically equivalent amount of the lead of the molten bathdisplaces the metal of the salt, which metal, reduced to the metallicstate, alloys directly with the remaining bath of molten lead. Thereaction precipitating the alloying metal is substantially a surfacereaction surface of the bath of molten lead and the dispersion of thealloying metal throughout the bath of lead depends upon the extent towhich the bath is agitated or stirred. The eventual uniform dispersionof the alloying metal or metals is therefore doubtful. The treatment isnecessarily carried out at temperatures appreciably above the meltingpoint of lead and substantial quantities of dross, which must beretreated, are produced.

We have discovered that such lead base alloys can be produced byelectrical means without encountering the disadvantages generallycontinwith the whole of the alloying metal being precipitated at theplane of contact. The alloying metal or metals are thus concentrated atthe gent upon the practice of the present art. The invention provides amethod for the addition and dispersion of metals of highermeltingtemperature into and throughout a bath of molten lead atreasonable temperatures substantially below the melting temperatures ofthe alloying metal or metals. Based on this discovery the inventioninvolves incorporating the alloying" metal or metals in the ionic statein a bath of molten lead by passing an electric current from an anode oranodes of the alloying metal or metals ,sub- T merged in a fusedelectrolyte through the fused; electrolyte to a bath of molten lead incontact with the fused electrolyte. Dispersion of the alloying metal sodeposited in the bath of molten lead throughout the bath is convenientlyeifected by appropriately stirring the molten metal.

In carrying out the invention, the,lead to be alloyed is melted and asuitable bath thereof is brought to the proper temperature. An anode oranodes of the substantially pure metal or metals to be alloyed with thelead is suspended in a suitable molten or fused electrolyte which is incontactwith the bath of molten lead. The

molten lead serves as a cathode. An E. M. F. is applied at theelectrodes in such a way as to cause an electric current to flow fromthe anodes to the fused electrolyte and through the fused electrolyte tothe molten lead cathode. As a result the alloying metal or metals areelectrically corroded from the anode or anodes and deposited in themolten lead cathode. The electrolyte may be any fused salt of a metaland an acid characterized in that the metal of the salt iselectropositive to the alloying metal or metals and the heat offormation of the metal of the salt and acid radical of the salt is equalto or higher than that of lead and the acid radical of the salt. Whenmore than one metal is to be alloyed with the lead, the electrolytesmust each conform to the foregoing characterization.

The single figure of the accompanying drawing diagrammaticallyillustrates an apparatus for the practice of the invention initssimplest form. It is to be understood that any number of electro lytecompartments may be used, each compart merit employing a similar ordissimilar anode and consequently a similar or dissimilar elec= trolyteand the common molten lead cathode. For the purposes of explanation, theinvention will be particularly described as applied to the production ofan alloy of lead and copper, but it is to be understood that alloys oflead with any one or more of the higher melting point metals commonlyassociated with or miscible with lead may be equally well produced andwith substantially the same advantages.

Referring to the drawing, the lead 3 to be alloyed is melted in asuitable not it and raised to a temperature of approximately 850 F. Thepot 8 may advantageously be an iron kettle. The fused electrolyte 2 isheld within a compartment formed by a vertically disposed open-endediron cylinder ll lined with refractory concrete. However, theelectrolyte compartment or compart ments may be constructed entirely oirefractory concrete or entirely of metal, and may be of any suitableshape. The cylinder 6 (r cylinders) is appropriately supported in avertical position with its lower edge submerged from 4 to 8 inches belowthe surface of the bath of molten lead 3.

The cylinder (or cylinders) is of such a length I as to allow about 1.5inches of length above the surface of the molten lead bath for each inchsubmerged in the molten lead. An anode i (or anodes) oi the metal (ormetals) to be alloyed with the lead is appropriately suspended in thefused electrolyte (or electrolytes) in such a man nor as to permitvertical adjustment of the anode (or anodes) with respect to the moltenlead cathode. The cathode connections may be made by an electricalconnection 5 to the pot 8 or by means of an electrode 4 extending intothe mol ten lead bath, or by both means. Where the pot 8 is an ironkettle, the cathode is preferably made to the kettle itself. The anode I(or anodes) and the cathode connections I or 5, or both, areelectrically connected to an electric generator G, or other suitablesource of electric energy.

In alloying copper with lead, the electrolyte is-preferablyiead chlorideto which may-be added alkali metal or alkaline earth or other metalchlorides, such as, sodium chloride, barium chloride, zinc chloride andthe like. Th function of the alkali metal or alkaline earth chlorides isto lower the melting point of the fused electrolyte and to increase itselectrical conductivity,

The electrolyte is preferably fused outside of the cell and thenadded-to the electrolyte compartment b. However, the electrolyte may bemelted by the heat of the molten lead bath 3 or by the resistance heatof the electric current. It is preferable to adjust the meltingtemperature of the electrolyte so that when passage of the electriccurrent is stopped, the fused electrolyte will solidify while the metalin the pot remains molten. Thus the electrolyte compartment containingthe solidified eleptrolyte may be lifted from the pot at the end of theoperation.

At the start of the operation the metal anode I (or anodes) is adjustedso that it is approximately one inch above the molten lead cathode andis covered by the fused electrolyte (or electrolytes). The current fromthe generator G, or other suitable source of electric energy, is thenstarted. The molten lead cathode is stirred connection from time to timeby a stirring device I. It has been found that stirring from 30 to 50%of the time is sufiicient to effect uniform dispersion of the alloyingmetal ionically deposited in the molten bath of lead. The electrolyte 2is maintained. in the molten or fused state by the resistance heat ofthe electric current and by the heat supplied by the molten leadcathode.

In alloying copper with lead in accordance with the invention using afused electrolyte consisting largely of lead chloride, the followingreactions take place:

Anode reaction: Cu+equivalent amount of electric current-*Cu+ Cathodereaction: Cu+-Cu+equivalent amount of electric current Electrolytereaction:

-Cu anode Cu+l I Cl- Pb cathode As a result of the anode reaction,cuprous chloride is formed at the a Immediately p being formed thecuprous chloride is dissociated into metallic copper ions which migrateto the cathode and chlorine ions which migrate to the anode. After theinitial anode reaction, the cuprous chloride, due to its lowerdecomposition voltage, becomes the real supporter of the electrolysis,and the process continues so long as the electric current is allowed toflow. The alloying metal or metals, copper in this instance, travels toand is deposited in the molten lead cathode in the ionic metallic state.The electrolyte is regenerated, and all actions are simultaneous andcontinuous.

'The only raw materials used in the process are the cathode lead to bealloyed and the anode metal or metals to be alloyed with the lead. Sincethe electrolyte is regenerated, it may be used continuously andrepeatedly. The following examples illustrate practices of theinvention:

Example Example #1 #2 Cathode metal to be alloyed (Pb) wt. lbs 9, 710 9,848 Average amperage. 70. 40 14 29 Average voltage 1. 84 3. 37 Time ofelectrolysis, hours 2p. 5 8. 66 Electrochemical equivalent, monovalcntCu gms. 11 per amp. hr.) 2. 3717 2. 3717 Copper deposited in lead,actual wt. lbs. .7..-l8 6.18 Copper deposited in lead, theoretical wt.7. 54 6. 58 Ampere efiicioncy, per cent 95. 4 93. 94 Dross formed duringtreatment, wt. lbs 40 30 Cathode metal temperature range, degrees R.820-920 Electrolyte temperature range, degrees F 740-840 720-780Electrolyte No. 1 No. 2

per cent" 60 ZnClz do 20 25 NaCh d 10 15 Analysis of metal beforeelectrolysis Cu Nil Nil Analysis of metal after electrolysis Cu 074 062The practice of the invention requires very little attention. The ampereefilciency is sub-- trol necessary for operation is a suitableinstrument for measuring the amperage.

The alloying metal or metals are deposited-in the molten lead as ions ofthe metal rather'than as particles, thereby making possible a better Thecost of thealloying metal added to the lead is substantially less whenused in the metallic form than when obtained from a salt or compound ofthe metal. For example, when copper is to be added to lead the cost ofthe copper in metallic form as employed in the practice of the presentinvention is considerably less than when obtained from copper salts,such as copper chloride or copper sulphate, as heretofore commonlyemployed in the production of alloys of lead and copper; The inventionthus effects a substantial economic saving.

While we have hereinbeforeparticularly de-' scribed the addition ofcopperto lead inorder to illustrate the electrolytic method of theinvention, it is to be understood that one or more of the high meltingpoint metallic elements such as copper, nickel, silver, tellurium, etc.,may be alloyed alone or 'at the same time with the lead I with equalfacility. When one or more additional metals are to' be alloyed with thelead, the apparatus may consist of multiple electrolyte compartments andmultiple anodes of the metals to be added. In this case, the electrolytecompartments may contain similar or dissimilar electrolytes as requiredby the particular anodes emmay thus be produced in a single operation orin one or more successive separate steps using the alloy from a previousoperation as the cathode in the succeeding operation.

We claim: V 1. The method of producing an alloy of lead and a metalhaving a substantially higher melting point than lead which comprisesincorporating the alloying metal into a molten bath of lead byelectrolytically transferring the alloying metal-from a solid anodethereof submerged in a fused electrolyte to a cathode consisting of. themolten bath of lead, said fused electrolyte conhigh as that of lead andthe acid radical of the salt.

2. The method of producing an alloy of lead and a metallic element ofthe group consisting of copper, nickel, tellurium and silver whichcomprises incorporating the alloying metallic element into a molten bathof lead by electrolyti ployed. Alloys of one or more metals with lead vcally transferring the alloying metallic element from a solid anodethereof submerged in a fused electrolyte to a cathode consisting of themolten bath of lead, said fused electrolyteconsisting essentially of asalt of a metal and an acid characterized in that the metal of the saltis electropositive to the metallic element to be alloyed with the leadand the heat of formation of the metal and the acid radical of the saltis at least as high as that of lead and the acid radical of the salt.

3. The method of producing an alloy of lead and copper which comprises,incorporating the copper in a molten bath of lead by electrolyticallytransferring the copper from a solid anode thereof submerged in a fusedelectrolyte consisting essentially of lead chloride to a cathodeconsisting of the molten bath of lead.

4. The method of producing an alloy of lead and atmetal. having asubstantially higher melting point than lead whichcomprises-incorporating the alloying metal into a molten bath .of leadby electrolytically transferring the alloying metal from a solid anodethereof submerged in a fused electrolyte to a cathode consisting of themolten bath of lead, said fused electrolyte consisting essentially of asalt of a metal and an acid characterized in that the metal of the saltis electro-. positive to the metal to be alloyed with the lead and theheat of formation of the metal and the acid radical of the salt is atleast as high as that of lead and the acid radical of the .salt, andincorporating a second metal having a substantially higher melting pointthan lead in a molten'bath of the alloy of lead and the first-V trolyteto a cathode consisting of the molten bath of alloy of lead and thefirst-mentioned alloying metal.

WILLIAM WALLACE SEROPSHIRE. AMSON L. FROHMAN.

